Scala example source code file (Reifiers.scala)

This example Scala source code file (Reifiers.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

none, none, notype, notype, reifier, reifyenvironment, some, string, symbol, symbol, tree, type, typeerror, typeerror

The Scala Reifiers.scala source code

package scala.tools.nsc
package transform

import scala.tools.nsc.symtab.SymbolTable
import scala.reflect
import collection.mutable.HashMap

/** Functions to reify (and un-reify) symbols, types, and trees.
 *  These can be used with only a symbol table; they do not
 *  need a full compiler.
 *
 *  @author Gilles Dubochet, Lex Spoon
 */
trait Reifiers {
  val symbols: SymbolTable
  import symbols._

  private def mkGlobalSymbol(fullname: String, sym: Symbol): reflect.Symbol =
    if (sym.isClass) reflect.Class(fullname)
    else if (sym.isType) reflect.TypeField(fullname, reify(sym.info))
    else if (sym.isMethod) reflect.Method(fullname, reify(sym.info))
    else if (sym.isValueParameter) reflect.LocalValue(reflect.NoSymbol, fullname, reify(sym.info))
    else reflect.Field(fullname, reify(sym.info));

  def reify(sym: Symbol): reflect.Symbol = {
    if (sym.isRoot || sym.isRootPackage || sym.isEmptyPackageClass || sym.isEmptyPackage)
      reflect.RootSymbol
    else if (sym.isValueParameter)
      mkGlobalSymbol(sym.name.toString, sym)
    else if (sym.owner.isTerm) 
      reflect.NoSymbol
    else reify(sym.owner) match {
      case reflect.NoSymbol => 
        reflect.NoSymbol;
      case reflect.RootSymbol =>
        mkGlobalSymbol(sym.name.toString(), sym)
      case reflect.Class(ownername) =>
        mkGlobalSymbol(ownername + "." + sym.name, sym)
      case _ =>
        reflect.NoSymbol
    }
  }

  var _log_reify_type_ = false

  def reify(tp: Type): reflect.Type = tp match {
    case ErrorType =>
      reflect.NoType
    case WildcardType =>
      if (_log_reify_type_) println("cannot handle WildcardType")
    reflect.NoType
    case NoType =>
      reflect.NoType
    case NoPrefix =>
      reflect.NoType
    case ThisType(sym) =>
      val rsym = reify(sym)
      reflect.ThisType(rsym)
    case SingleType(pre, sym) =>
      reflect.SingleType(reify(pre), reify(sym))
    case ConstantType(value) =>
      reify(value.tpe)
    case TypeRef(pre, sym, args) =>
      val rpre = reify(pre)
      val rsym = reify(sym)
      val rargs = args map reify
      val beforeArgs = reflect.PrefixedType(rpre, rsym)
      if (rargs.isEmpty)
	beforeArgs
      else if (rpre == reflect.NoType || rsym == reflect.NoSymbol)
	beforeArgs
      else
	reflect.AppliedType(beforeArgs, rargs)
    case TypeBounds(lo, hi) =>
      reflect.TypeBounds(reify(lo), reify(hi))
    case RefinedType(parents, defs) =>
      if (_log_reify_type_) println("cannot handle RefinedType "+tp); reflect.NoType
    case ClassInfoType(parents, defs, clazz) =>
      if (_log_reify_type_) println("cannot handle ClassInfoType "+tp); reflect.NoType
    case MethodType(params, result) =>
      reflect.MethodType(params.map(reify), reify(result))
    case NullaryMethodType(result) =>
      reflect.NullaryMethodType(reify(result))
    case PolyType(tparams, result) =>
      val boundss =
	for {
	  param <- tparams
	  TypeBounds(lo,hi) = param.info.bounds
	} yield (reify(lo), reify(hi))
	  
      reflect.PolyType(
	tparams.map(reify),
	boundss,
	reify(result))
      //todo: treat ExistentialType
    case AnnotatedType(annots, tp, _) =>
      reify(tp)
    case _ =>
      println("could not reify: " + tp)
      reflect.NoType
  }


  /** This is woefully incomplete.  It is barely enough
   *  to process the types of Constant's .
   */
  def unreify(tpe: reflect.Type): Type =
    tpe match {
      case reflect.NoPrefix => NoPrefix
      case reflect.NoType => NoType
      case reflect.NamedType(fullname) =>
	//NamedType(fullname)
	println("NamedType: " + fullname)
	NoType
      case reflect.PrefixedType(_, reflect.Class("scala.Array")) =>
        definitions.ArrayClass.tpe
      case reflect.PrefixedType(_, reflect.Class("java.lang.String")) =>
        definitions.StringClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Unit")) =>
        definitions.UnitClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Boolean")) =>
        definitions.BooleanClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Byte")) =>
        definitions.ByteClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Short")) =>
        definitions.ShortClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Int")) =>
        definitions.IntClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Long")) =>
        definitions.LongClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Float")) =>
        definitions.FloatClass.tpe
      case reflect.PrefixedType(_, reflect.Class("scala.Double")) =>
        definitions.DoubleClass.tpe
      case reflect.PrefixedType(pre, sym) => 
	NoType
      case reflect.SingleType(pre, sym) => 
	SingleType(unreify(pre), unreify(sym))
      case reflect.ThisType(clazz) => 
	ThisType(unreify(clazz))
      case reflect.AppliedType(tpe, args) => 
	val untpe = unreify(tpe)
	if (untpe == NoType)
	  NoType
	else
	  appliedType(untpe, args.map(unreify))
      case reflect.TypeBounds(lo, hi) => 
	TypeBounds(unreify(lo), unreify(hi))
      case reflect.MethodType(params, restpe) =>
	MethodType(params.map(unreify), unreify(restpe))
      case reflect.NullaryMethodType(restpe) =>
	NullaryMethodType(unreify(restpe))
      case reflect.PolyType(typeParams, typeBounds, resultType) =>
	PolyType(typeParams.map(unreify), unreify(resultType))
      //todo: treat ExistentialType
      case _ => NoType
    }


  /** This is woefully incomplete.  It is barely enough
   *  to process the types of Constant's .
   */
  def unreify(symbol: reflect.Symbol): Symbol =
    symbol match {
      case reflect.Class(fullname) => 
	fullname match {
	  case "scala.Unit" => definitions.UnitClass
	  case "scala.Boolean" => definitions.BooleanClass
	  case "scala.Byte" => definitions.ByteClass
	  case "scala.Short" => definitions.ShortClass
	  case "scala.Int" => definitions.IntClass
	  case "scala.Long" => definitions.LongClass
	  case "scala.Float" => definitions.FloatClass
	  case "scala.Double" => definitions.DoubleClass

	  case "scala.Array" => definitions.ArrayClass

	  case _ => NoSymbol

	}

      case _ => NoSymbol
    }

  case class FreeValue(tree: Tree) extends reflect.Tree

  class ReifyEnvironment extends HashMap[Symbol, reflect.Symbol] {
    var targets = new HashMap[String, Option[reflect.LabelSymbol]]()
    def addTarget(name: String, target: reflect.LabelSymbol): Unit =
      targets.update(name, Some(target))
    def getTarget(name: String): Option[reflect.LabelSymbol] =
      targets.get(name) match {
        case None =>
          targets.update(name, None)
          None
        //case Some(None) => None //bq:redundant
        case Some(tgt) => tgt
      }
    def hasAllTargets: Boolean =
      targets.iterator.map(_._2).forall {
        case Some(_) => true
        case None => false
      }
    override def update(sym: Symbol, rsym: reflect.Symbol) =
      super.update(sym,rsym)
  }

  
  class Reifier(env: ReifyEnvironment, currentOwner: reflect.Symbol)
  {
    def reify(tree: Tree): reflect.Tree = tree match {
      case Ident(_) =>
        val rsym = reify(tree.symbol);
        //Console.println("LiftCode: seen ident")
        if (rsym == reflect.NoSymbol) {
          //Console.println("  free = "+tree)
          FreeValue(tree)
        } else {
          //Console.println("  rsym = "+rsym)
          reflect.Ident(rsym)
        }
      case Select(qual, _) =>
        val rsym = reify(tree.symbol);
        if (rsym == reflect.NoSymbol) throw new TypeError("cannot reify symbol: " + tree.symbol)
        else reflect.Select(reify(qual), reify(tree.symbol))

      case Literal(constant) =>
        reflect.Literal(constant.value)

      case Apply(name, args) if name.toString().startsWith("label$") =>
        env.getTarget(name.toString()) match {
          case None => throw new TypeError("cannot reify tree (no forward jumps allowed): " + tree)
          case Some(label) => reflect.Goto(label)
        }

      case Apply(fun, args) =>
        reflect.Apply(reify(fun), args map reify)

      case TypeApply(fun, args) =>
        reflect.TypeApply(reify(fun), args map (_.tpe) map reify)

      case Function(vparams, body) =>
        var env1 = env
        for (vparam <- vparams) {
          val local = reflect.LocalValue(
            currentOwner, vparam.symbol.name.toString(), reify(vparam.symbol.tpe));
          env1.update(vparam.symbol, local);
        }
        reflect.Function(vparams map (_.symbol) map env1, 
                         new Reifier(env1, currentOwner).reify(body))
      case tree@This(_) if tree.symbol.isModule =>
        // there is no reflect node for a module's this, so
        // represent it as a selection of the module
	reify(
	  Select(This(tree.symbol.owner), tree.symbol.name))
      case This(_) => 
        reflect.This(reify(tree.symbol))
      case Block(stats, expr) => 
        reflect.Block(stats.map(reify), reify(expr))
      case New(clazz) if (clazz.isType) =>
	val reifiedSymbol = reify(clazz.symbol)
	reflect.New(reflect.Ident(reifiedSymbol))
      case New(clazz) =>
        val reifiedClass = reify(clazz)
        reflect.New(reifiedClass)
      case Typed(t, _) =>
        reify(t)
      case If(cond, thenp, elsep) =>
        reflect.If(reify(cond), reify(thenp), reify(elsep))
      case Assign(lhs, rhs) =>
        reflect.Assign(reify(lhs), reify(rhs))

      case LabelDef(name, Nil, body) =>
        val sym = new reflect.LabelSymbol(name.toString())
        env.addTarget(name.toString(), sym)
        val res = reflect.Target(sym, reify(body))
        res

      case vd @ ValDef(mods, name, tpt, rhs) =>
        val rtpe = reify(vd.tpe) // will return null, currently?!
        val sym  = reflect.LocalValue(currentOwner, name.toString(), rtpe)
        env(vd.symbol) = sym // bq: despite Scala's scoping rules, this should work because references to vd.symbol were type checked.
        val rhs_ = reify(rhs)
        reflect.ValDef(sym, rhs_)

      case cd @ ClassDef(mods, name, tparams, impl) => 
        if(!tparams.isEmpty) 
          throw new TypeError("cannot handle polymorphic ClassDef ("+name+"): " + tparams)
        val rsym = reify(cd.symbol)
        val rimp = reify(impl)
        val rtpe = reify(impl.self.tpt.tpe) //todo: update
        reflect.ClassDef(rsym, rtpe, rimp.asInstanceOf[reflect.Template])

      case tmpl @ Template(parents, self, body) =>
        val rparents = for (p <- parents) yield { reify(p.tpe) }
        //todo: add self to reified templates
        reflect.Template(rparents, body.map(reify))

      case dd @ DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
        if(!tparams.isEmpty) 
          throw new TypeError("cannot handle polymorphic DefDef ("+name+"): " + tparams)
        val rsym   = reify(dd.symbol)
        val rparss = vparamss map { x => x map (reify) }
        val rret   = reify(tpt.tpe)
        val rrhs   = reify(rhs)
        reflect.DefDef(rsym, rparss, rret, rrhs)

      case sp @ Super(qual, mix) =>
        val rsym = reify(sp.symbol)
        reflect.Super(rsym)

      case _ =>
        throw new TypeError("cannot reify tree ("+tree.getClass()+"): " + tree)
    }

    def reify(sym: Symbol): reflect.Symbol =
      env.get(sym) match {
	case Some(rsym) => 
	  rsym
	case None =>
	  Reifiers.this.reify(sym)
      }

    def reify(tpe: Type): reflect.Type =
      Reifiers.this.reify(tpe)
  }

  def reify(tree: Tree): reflect.Tree =
    new Reifier(new ReifyEnvironment(), reflect.NoSymbol).reify(tree)
}